function myReduce(cb, initionalValue) {
    var _arr = this;
    var _len = _arr.length;
    var _arg3 = arguments[2] || window;

    for(var i = 0; i < _len; i++) {
        initionalValue = cb.apply(_arg3, [initionalValue, _arr[i], i, _arr]);
    }
    return initionalValue;
}